In sensors such as a position sensor, a brush-like slider 100 as shown in FIG. 8, for example, is used in order to send and receive electrical signals, power, etc. between a member on the main body side of a sensor and an assembly (a part) which performs movements, such as rotational or linear movements, with respect to this member. In this slider 100, a sliding contact 10 in the tip portion of the slider which comes into sliding contact with a rotor etc. is an important part. The sliding contact 10 is used in a condition brought into sliding contact with an object of contact in the tip portion of each finger 12a which constitutes a brush 12, and it is preferred that the tip portion of the finger 12a be slidable as smoothly as possible. In view of this point, in the manufacturing of the sliding contact 10, the surface of the tip portion of the finger 12a may sometimes be worked to provide a curved surface.
For example, there is a method of manufacturing a sliding contact by blanking in press working as a method of relatively easily manufacturing a sliding contact. Schematically, this method involves fabricating sliding contact pieces having unbent tip portions (refer to sliding contact pieces 10′ in FIG. 1) by the press working of a sheet material for sliding contacts and fabricating a sliding contact by further performing working. However, in the case of blanking, the periphery of the tip portion of a finger of a brush may sometimes become sharp or a burr may sometimes occur on this periphery (refer to FIG. 2(b)). If the tip portion of a finger is sharp or the periphery has a burr, it may be impossible to cause the tip portion of the brush 12 to slide smoothly, with the tip portion of the brush 12 kept in contact with an object of contact. Therefore, in the case of blanking, the tip portion of a finger of a brush of a sliding contact piece obtained by blanking is polished and worked to provide a curved surface thereby ensuring smooth sliding.
Barrel polishing is used as a method of polishing the tip portion of the finger 12a of the brush 12. Usually, the sliding contact (sliding contact piece) 10 has an about 15×15 mm size. This is because this size is suitable for performing barrel polishing, with the sliding contact put in the vessel of a barrel polishing machine. Furthermore, this is because the tip portion of a finger to be polished usually has a size of 0.1 mm (thickness)×0.4 mm (width) or a minute region smaller than this and it is difficult to polish only this part, which is possible when barrel polishing is performed.
Incidentally, in barrel polishing, a polishing medium, such as a polishing stone, and a sliding contact piece are put in the vessel of a barrel polishing machine and the whole peripheral surface of the sliding contact piece is polished by rotating the vessel. That is, in barrel polishing it is impossible to polish only the tip portion of the finger of the brush in a concentrated manner. Therefore, when barrel polishing is adopted, it is difficult to positively polish the tip portion until a sufficiently smooth state is obtained and besides variations are apt to occur in the polished state.
And some sliding contact pieces (sliding contacts) are made of a sheet material and such sliding contact pieces (sliding contacts) may sometimes be deformed due to the force received from the polishing medium during barrel polishing. Because deformed materials cannot be made as products, the problem of a decrease in the product yield arises.
However, when sliding contact pieces are to be barrel polished, it is necessary that the sliding contact pieces be beforehand brought into a state capable of being put in the vessel by separating the sliding contact pieces as a unit into individual ones. However, when once the sliding contact pieces as a unit are separated, the sliding contacts (sliding contact pieces) become less easy to handle after that. For example, it takes time and labor when the sliding contacts (sliding contact pieces) are to be aligned in the same direction and when the number of sliding contacts is to be counted. Therefore, from the standpoint of handling of sliding contacts, it is preferable to use a strip material in which a plurality of sliding contact pieces stretch in line (refer to the strip material of sliding contact pieces shown in FIG. 1). This is because transfer and counting are easy when a plurality of sliding contacts stretch as a unit. Furthermore, this is because when sliders are automatically continuously manufactured, sliding contacts can be continuously fed easily and rapidly if strip-like sliding contact pieces can be used.